With the development of Internet, the amount of delivery of documents and data by electronic mail (e-mail) has increased. However, fax is still widely used as a means for delivering documents with legal force. In addition, with the development of Information Technology (IT), various functions and services linked with fax, such as web fax services that makes up for the disadvantage of existing normal fax by allowing data to be transmitted from a fax to an e-mail account or vice versa, have been increasingly developed and provided.
However, when documents are delivered by fax, it is difficult to manage delivered fax documents in an integrated manner. When a fax solution like a web fax service is used, fax data transmitted and received using a web fax server can be managed in the integrated manner, but fax data transmitted and received by a normal fax machine cannot be managed in the integrated manner. Moreover, in conventional fax solutions, a lot of public switched telephone network (PSTN) lines need to be connected to a web fax server, which makes installation difficult and restricted by space.